HTTP URL Rewrite
The URL rewriting feature provides FSM Gateway users with a way to modify the request URL before the traffic enters the target service. This not only provides greater flexibility to adapt to changes in backend services, but also ensures smooth migration of applications and normalization of URLs.
The HTTPRoute resource utilizes HTTPURLRewriteFilter to rewrite the path in request to another one before it gets forwarded to upstream.
Prerequisites
- Kubernetes cluster version v1.21.0 or higher.
- kubectl CLI
- FSM Gateway installed via guide doc.
Demonstration
We will follow the sample in HTTP Routing.
In backend server, there is a path /get which will responds more information than path /headers.
curl -H 'host:foo.example.com' http://$GATEWAY_IP:8000/get
{
"args": {},
"headers": {
"Accept": "*/*",
"Connection": "keep-alive",
"Host": "foo.example.com",
"User-Agent": "curl/7.68.0"
},
"origin": "10.42.0.87",
"url": "http://foo.example.com/get"
}
Replace URL Full Path
Example bellow will replace the /get path to /headers path.
kubectl apply -n httpbin -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
name: http-route-foo
spec:
parentRefs:
- name: simple-fsm-gateway
port: 8000
hostnames:
- foo.example.com
rules:
- matches:
- path:
type: PathPrefix
value: /get
filters:
- type: URLRewrite
urlRewrite:
path:
type: ReplaceFullPath
replaceFullPath: /headers
backendRefs:
- name: httpbin
port: 8080
- matches:
- path:
type: PathPrefix
value: /
backendRefs:
- name: httpbin
port: 8080
EOF
After updated the HTTP rule, we will get the same response as /headers when requesting /get.
curl -H 'host:foo.example.com' http://$GATEWAY_IP:8000/get
{
"headers": {
"Accept": "*/*",
"Connection": "keep-alive",
"Host": "foo.example.com",
"User-Agent": "curl/7.68.0"
}
}
Replace URL Prefix Path
In backend server, there is another two paths:
/status/{statusCode}will respond with specified status code./stream/{n}will respond the response of/getntimes in stream.
curl -s -w "%{response_code}\n" -H 'host:foo.example.com' http://$GATEWAY_IP:8000/status/204
204
curl -s -H 'host:foo.example.com' http://$GATEWAY_IP:8000/stream/1
{"url": "http://foo.example.com/stream/1", "args": {}, "headers": {"Host": "foo.example.com", "User-Agent": "curl/7.68.0", "Accept": "*/*", "Connection": "keep-alive"}, "origin": "10.42.0.161", "id": 0}
If we hope to change the behavior of /status to /stream, the rule is required to update again.
kubectl apply -n httpbin -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
name: http-route-foo
spec:
parentRefs:
- name: simple-fsm-gateway
port: 8000
hostnames:
- foo.example.com
rules:
- matches:
- path:
type: PathPrefix
value: /status
filters:
- type: URLRewrite
urlRewrite:
path:
type: ReplacePrefixMatch
replacePrefixMatch: /stream
backendRefs:
- name: httpbin
port: 8080
- matches:
- path:
type: PathPrefix
value: /
backendRefs:
- name: httpbin
port: 8080
EOF
If we trigger the request to /status/204 path again, we will stream the request data 204 times.
curl -s -H 'host:foo.example.com' http://$GATEWAY_IP:8000/status/204
{"url": "http://foo.example.com/stream/204", "args": {}, "headers": {"Host": "foo.example.com", "User-Agent": "curl/7.68.0", "Accept": "*/*", "Connection": "keep-alive"}, "origin": "10.42.0.161", "id": 99}
...
Replace Host Name
Let’s follow the example rule below. It will replace host name from foo.example.com to baz.example.com for all traffic requesting /get.
kubectl apply -n httpbin -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
name: http-route-foo
spec:
parentRefs:
- name: simple-fsm-gateway
port: 8000
hostnames:
- foo.example.com
rules:
- matches:
- path:
type: PathPrefix
value: /get
filters:
- type: URLRewrite
urlRewrite:
hostname: baz.example.com
backendRefs:
- name: httpbin
port: 8080
- matches:
- path:
type: PathPrefix
value: /
backendRefs:
- name: httpbin
port: 8080
EOF
Update rule and trigger request. We can see the client is requesting url http://foo.example.com/get, but the Host is replaced.
curl -H 'host:foo.example.com' http://$GATEWAY_IP:8000/get
{
"args": {},
"headers": {
"Accept": "*/*",
"Connection": "keep-alive",
"Host": "baz.example.com",
"User-Agent": "curl/7.68.0"
},
"origin": "10.42.0.87",
"url": "http://baz.example.com/get"
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